Human papillomavirus (HPV) types 6 and 11 are the causative agents for more than 90% of all genital condyloma and laryngeal papillomas. HPV is a DNA virus which is enclosed in a capsid which is made up principally of L1 protein. The L1 proteins of HPV types 6 and 11 are very similar at both the amino acid and nucleotide level. Consequently, it has been difficult to develop assays which reliably distinguish between these two types of infection.
HPV 11 L1 residues Gly131-Tyr132 were previously identified as responsible for the type-specific binding of several HPV 11 neutralizing monoclonal antibodies (Ludmerer et. al. 1996. “Two Amino Acid Residues Confer Type Specificity to a Neutralizing, Conformationally Dependent Epitope on Human Papillomavirus Type 11”. J. Virol. 70:4791–4794). Within this same work, it was further demonstrated that a substitution at Ser346 of the HPV 11 L1 sequence dramatically reduced binding of neutralizing monoclonal antibody H11.H3, and that the effect was specific for this antibody. Additional studies demonstrated that several HPV 11 neutralizing antibodies bound to a stretch of the HPV 11 L1 sequence between residues 120–140, whereas H11.H3 bound to a completely distinct site (Ludmerer et al. 1997. “A Neutralizing Epitope of Human Papillomavirus Type 11 is Principally Described by a Continuous Set of Residues Which Overlap a Distinct Linear, Surface-Exposed Epitope”. J. Virol. 71:3834–3839).
However, these studies did not define which amino acid residues confer type specificity of binding for antibody H11.H3 completely. Furthermore, there may be other regions of HPV 11 VLPs, not described in these studies, which can elicit important HPV 11-specific, conformationally dependent responses. In addition, VLP-dependent antibodies specific for HPV 6 have also been generated (Christensen et al. 1996 “Monoclonal Antibodies to HPV-6 L1 Virus-Like Particles Identify Conformational and Linear Neutralizing Epitopes on HPV-11 in Addition to Type-Specific Epitopes on HPV-6”. Virology 224(2):477–486). These antibodies could be useful in evaluation of infectivity by HPV 6. It would be desirable to determine the exact amino acids involved in the specificity of HPV type 6- and additional type 11-specific conformational epitope formations so that improved assays and vaccines may be developed.